Regulation of heavy metals accumulated by Acorus calamus L. in constructed wetland through different nitrogen forms.

Improving accumulation of heavy metals (HMs) by plants is an important pathway for constructed wetland (CW) to alleviate the environmental risks caused by their release. This study aims to regulate HMs (Cr, Ni, Cu, Zn, and Cd) accumulated by Acorus calamus L. in the sandy substrate CW with different nitrogen forms, including ammonia (NH4+), nitrate (NO3‾), and NH4+/NO3‾ (1:1) in synthetic tailwaters. In general, the removal efficiency of HMs by CW could reach 92.4% under the initial concentrations below 500 µg/L. Accumulation percentages of HMs in the shoots and roots of plants in CW with NH4+ and NH4+/NO3‾ influents increased by 52-395% and 15-101%, respectively, when compared with that of NO3‾ treatment. Influents with NH4+ promoted plant growth of Acorus calamus L. and metabolic functions, such as carbohydrate metabolism/amino acid metabolism, related to HMs mobilization of rhizosphere bacterial communities, which might induce more organic acids and amino acids secreted by plants and microbes during their metabolic processes. These are the main reasons for the enhancive mobilization of HMs from their precipitation fractions and their uptake by plants in CW with NH4+ treatments. Moreover, the enhancement of organics secreted from plants and microbes also led to the high denitrification efficiency and nitrogen removal in CW. Overall, this study could provide a feasible method for the enhancive accumulation of HMs by wetland plants via the regulation water treatment process to appropriately increase NH4+ for CW.

Morphological and transcriptional responses of Lycopersicon esculentum to hexavalent chromium in agricultural soil.

The carcinogenic, teratogenic, and mutagenic effects of hexavalent chromium (Cr[VI]) on living organisms through the food chain raise the immediate need to assess the potential toxicological impacts of Cr(VI) on human health. Therefore, the concentration-dependent responses of 12 Cr(VI)-responsive genes selected from a high-throughput Lycopersicon esculentum complementary DNA microarray were examined at different Cr concentrations. The results indicated that most of the genes were differentially expressed from 0.1 mg Cr/kg soil, whereas the lowest-observable-adverse-effect concentrations of Cr(VI) were 1.6 mg Cr/kg soil, 6.4 mg Cr/kg soil, 3.2 mg Cr/kg soil, and 0.4 mg Cr/kg soil for seed germination, root elongation, root biomass, and root morphology, respectively, implying that the transcriptional method was more sensitive than the traditional method in detecting Cr(VI) toxicity. Dose-dependent responses were observed for the relative expression of expansin (p = 0.778), probable chalcone-flavonone isomerase 3 (p = -0.496), and 12S seed storage protein CRD (p = -0.614); therefore, the authors propose the 3 genes as putative biomarkers in Cr(VI)-contaminated soil. Environ Toxicol Chem 2016;35:1751-1758. © 2015 SETAC.

Spatial variations in daily average CO2 concentrations above wetland surface of Xianghai National Nature Reserve, China.

Horizontal and vertical variations of daily average CO2 concentration above the wetland surface were studied in Xianghai National Nature Reserve of China in August, 2000. The primary purpose was to study spatial distribution characteristics of CO2 concentration on the four levels of height(0.1 m, 0.6 m, 1.2 m and 2 m) and compare the differences of CO2 concentration under different land covers. Results showed that daily average CO2 concentration above wetland surface in Xianghai National Natural Reserve was lower than that above other wetlands in northeast China as well as the worldwide average, suggesting that Xianghai wetland absorbed CO2 in August and acted as "sink" of CO2. The horizontal variations on the four levels of height along the latitude were distinct, and had the changing tendency of "decreasing after increasing" with the increase of height. The areas with obvious variations were consistent on different levels of height, and those with the highest variations appeared above surface of shore, sloping field, Typha wetland and Phragmites wetland; the vertical variations were greatly different, with the higher variations in Phragmites wetland and Typha wetland, and the lands near the shore and the sloping field with the lower variations. Spatial variations of daily average CO2 concentrations above wetland surface were affected by surface qualities and land covers.

Spatial variations of Pb in the vertical zone of the soil-plant system in the Changbai Mountain National Nature Reserve.

The characteristics of vertical and horizontal variations of lead element(Pb) in soil-plant system of vertical zone in Changbai Mountain National Nature Reserve(CNNR) were studied. The results showed that Pb concentrations in soils of vertical zone are all above 25 mg/kg, and the average Pb concentration of each soil zone negatively correlates its degree of variation, i.e. brown coniferous forest soil zone has the lowest average Pb concentration of four soil zones, and the highest horizontal variation; however, mountain soddy forest soil has the highest average Pb concentration, and the lowest horizontal variation; the average concentration of plant Pb of each plant zone is lower than the worldwide average level of Pb in plant(Clarke), respectively, and plant Pb content order is consistent with soil Pb content order, but their horizontal variations are different from those in soil zones, the variation of mountain tundra forest zone is highest, but Betula ermanii forest zone the lowest. Vertical variation of plant Pb is obviously higher than that in soils with variation coefficient of 89.76%; the enrichment capability of plant for Pb is depended on the plant types and the different organs of plant; parent material and parent rock, pH values, soil organic matter and soil particle fraction etc. are the main factors influencing variations of Pb content in soil-plant system of vertical zone in CNNR.